1. Technical Field
The present invention relates to technology for driving data lines using a demultiplexer.
2. Related Art
Recently, in electronic devices such as cellular phones or navigation systems, technology for displaying high-definition images has been developed. The high-definition images can be achieved by increasing the number of scan lines and the number of data lines so as to increase the number of pixels, and in such a case, there is a problem in connections in the display panels. For example, when color display of vertical 320 dots×horizontal 240 dots is to be performed, total 720 data lines for 240 dots×3 colors are required in a horizontal direction of the display panel, but when the size of a display image is small, the pitches of the data lines become below the limit for COG (chip on glass) or the like, and accordingly, X drivers that supplies data signals to the data lines cannot be connected to the data lines.
Thus, a so-called hybrid method in which the 720 data lines, when the above-described display panel is used, are divided into groups, for example, each having three data lines, data signals for the three data lines belonging to each group are provided by using a time-division method, and a demultiplexer for sequentially selecting one data line from among the three data lines at a time and supplying data signals to the selected data line is formed integrally with pixel switching elements of the display panel has been proposed (for example, see JP-A-6-138851 (for example, FIG. 1)). By using this hybrid method, the number of input terminals of the demultiplexer decreases to ⅓ of the number of the data lines so as to loosen the connection pitches, and accordingly, it can be performed easily to mount the X drivers in the display panel.
In addition, in JP-A-6-138851, an example in which the number of input terminals of the demultiplexer is configured to be half the number of the data lines is described.
However, when switching elements constituting the demultiplexer are formed by using transistors, large transistors are required so as to decrease ON resistance of the transistors. In particular, when the switching elements are formed by amorphous silicon type thin film transistors having a low mobility, very large transistors are required. Since an area for forming the demultiplexer is an outer frame of a display area, so-called a frame size becomes large, and accordingly, there is a limitation on exterior design of the electronic device into which a display panel is inserted.